The United States has intervened in the debate over Britain’s membership of the European Union, declaring a “profound interest” in the UK remaining a part of the 28-member bloc.
Speaking days before EU leaders gather at a crucial summit in Brussels to thrash out David Cameron’s renegotiation demands, Mr Kerry said: “Obviously, the United States has a profound interest in your success, as we do in a very strong UK staying in a strong EU.
“The truth is, in every decade since its founding, the EU has been tested by forces - internal and external - that benefited from a house divided… We know many Europeans feel overwhelmed by the latest round of challenges, including concerns about the UK's potential exit from the EU.
"I want to express the confidence of the United States... that - as it has so many times before - Europe is going to emerge stronger than ever, provided it stays united and builds common responses to these challenges."
Mr Kerry’s intervention comes as Mr Cameron prepares to convince his 27 EU counterparts to sign off his renegotiation demands at a crucial leaders’ summit in Brussels.
AFP reported the Secretary of State as adding that the mass influx of refugees and migrants entering the continent spells a “near existential threat” to Europe.
"The United States understands the near existential nature of this threat to the politics and fabric of life in Europe," he reportedly told the Munich Security Conference.
"We are not saying 'this is your problem, not ours'," he added. "This is our problem... And that is why we are joining now and enforcing a NATO mission to close off a key access route and we will join you in other ways to stem this tide."
The annual Munich conference is one known for frank talk among top officials, and participants this year include Mr Kerry, French Prime Minister Manuel Valls, Ukrainian President Petro Poroshenko, Russian Foreign Minister Sergey Lavrov, British Foreign Minister Philip Hammond, and many others.